The present invention relates to a stent delivery system for use at a vessel bifurcation. More particularly, the present invention relates to a catheter assembly and method for assisting in the accurate delivery of an angulated stent into an acutely angulated side branch vessel for treatment thereof in a percutaneous transluminal coronary angioplasty (PTCA) procedure.
Stents conventionally repair blood vessels that are diseased. Stents are generally hollow and cylindrical in shape and have terminal ends that are generally perpendicular to their longitudinal axes. In use, the conventional stent is positioned at the diseased area of a vessel and, after placement, the stent provides an unobstructed pathway for blood flow.
Repair of vessels that are diseased at a bifurcation is particularly challenging since the stent must overlay the entire diseased area at the bifurcation, yet not itself compromise blood flow. Therefore, the stent must, without compromising blood flow, overlay the entire circumference of the ostium to a diseased portion and extend to a point within and beyond the diseased portion. Where the stent does not overlay the entire circumference of the ostium to the diseased portion, the stent fails to completely repair the bifurcated vessel. Where the stent overlays the entire circumference of the ostium to the diseased portion, yet extends into the junction comprising the bifurcation, the diseased area is repaired, but blood flow may be compromised in other portions of the bifurcation. Unopposed stent elements may promote lumen compromise during neointimalization and healing, producing restenosis and requiring further procedures. Moreover, by extending into the junction comprising the bifurcation, the stent may block access to portions of the bifurcated vessel that require performance of further interventional procedures. Similar problems are encountered when vessels are diseased at their angled origin from the aorta as in the ostium of a right coronary or a vein graft. In this circumstance, a stent overlaying the entire circumference of the ostium extends back into the aorta, creating problems, including those for repeat catheter access to the vessel involved in further interventional procedures.
Conventional stents are designed to repair areas of blood vessels that are removed from bifurcations and, since a conventional stent generally terminates at right angles to its longitudinal axis, the use of conventional stents in the region of a vessel bifurcation may result in blocking blood flow of a side branch or fail to repair the bifurcation to the fullest extent necessary. The conventional stent might be placed so that a portion of the stent extends into the pathway of blood flow to a side branch of the bifurcation or extend so far as to completely cover the path of blood flow in a side branch. The conventional stent might alternatively be placed proximal to, but not entirely overlaying, the circumference of the ostium to the diseased portion. Such a position of the conventional stent results in a bifurcation that is not completely repaired. The only conceivable situation in which the conventional stent, having right-angled terminal ends, could be placed where the entire circumference of the ostium is repaired without compromising blood flow, is where the bifurcation is formed of right angles. In such scenarios, extremely precise positioning of the conventional stent is required. This extremely precise positioning of the conventional stent may result with the right-angled terminal ends of the conventional stent overlaying the entire circumference of the ostium to the diseased portion without extending into a side branch, thereby completely repairing the right-angled bifurcation.
To circumvent or overcome the problems and limitations associated with conventional stents in the context of repairing diseased bifurcated vessels, an angulated stent that consistently overlays the entire circumference of the ostium to a diseased portion, yet does not extend into the junction comprising the bifurcation, may be employed. Unlike the conventional stents described above which terminate at right angles to its longitudinal axis, an angulated stent terminates at various angles depending upon and corresponding to the angulation of the bifurcated ostium. An angulated stent is designed to match the angle of the ostium of the branch and therefor offers maximum coverage. An angulated stent would have the advantage of completely repairing the vessel at the bifurcation without obstructing blood flow in other portions of the bifurcation. In addition, such a stent would allow access to all portions of the bifurcated vessel should further interventional treatment be necessary. In a situation involving disease in the origin of an angulated aorto-ostial vessel, such a stent would have the advantage of completely repairing the vessel origin without protruding into the aorta or complicating repeat access.
In addition to the problems encountered by using the prior art stents to treat bifurcations, the delivery platform for implanting angulated stents has presented numerous problems. The major issues for this type of delivery system are centered on the translational and rotational orientation of the stent at the time of deployment. As current stent and delivery systems are used to treat these lesions, the translation problem of locating the stent precisely at the ostium is compounded by the effect of improper placement. Current methods for conventional stent placement rely heavily on the catheter design, which has been shown to be relatively effective in straight or non-branched anatomy. However, in areas of bifurcation these conventional methods have proven to be less effective.
Because an angulated stent is designed to match the angle of the ostium of the branch, proper rotational orientation is critical. While visualizing the delivery system is not a critical issue, precise positioning of the angulated stent in a specific location, such as a carina, using two dimensional images of a three dimensional anatomy poses a tremendous challenge.
One prior art device used to deliver an angulated stent is a bifurcation lesion stent system that utilizes a dual guide wire catheter for placement of an angulated stent. An angulated stent is pre-mounted on a balloon and is delivered over a routine angioplasty guide wire, the tracking guide wire, down the side branch allowing the stent system to track down the branch. A second positioning guide wire is placed down a separate lumen and on the balloon surface such that it turns away from the balloon at an angle just proximal to the stent. Once located at a bifurcation, the tracking wire is advanced down the side branch and the stent positioning guide wire is advanced down the primary vessel. Once the stent delivery balloon has been positioned in the branch vessel, then the stent is positioned in an appropriate position at the ostium of the side branch. The stent is deployed at the ostium of the side branch using the positioning wire to ensure optimal location of the stent. If the stent were misaligned with the ostium of the side branch, the positioning wire would provide torque on the delivery catheter and would not allow advancement of the balloon into the correct position unless the stent system were rotated appropriately.
Attempts to deliver any device, such as an angulated stent on a balloon assembly to a bifurcation over two wires are prone to the problem of wire wrapping. The resulting wrapping then creates resistance to advancement of the device, thus resulting in failure of deployment. Therefore, when delivering a device ultimately utilizing two wires, it would be desirable to first achieve proper rotational orientation prior to entrance into the target vessel. The present invention offers a solution to these problems and others.
As used herein, the terms xe2x80x9cproximal,xe2x80x9d xe2x80x9cproximally,xe2x80x9d and xe2x80x9cproximal directionxe2x80x9d when used with respect to the invention are intended to mean away from or out of the patient, and the terms xe2x80x9cdistal,xe2x80x9d xe2x80x9cdistally,xe2x80x9d and xe2x80x9cdistal directionxe2x80x9d when used with respect to the invention are intended to mean toward or into the patient. These definitions will apply with reference to apparatus, such as catheters, guide wires, stents, and the like.
What is needed and heretofore unavailable is a catheter assembly that allows for accurate placement and deployment of an angulated stent in an acutely angulated side branch vessel at a bifurcation. The present invention satisfies these and other needs.
The invention provides for an improved catheter assembly and method of use for assisting in the delivery of an angulated stent into an acutely angulated side branch vessel for the purpose of accurate placement of the angulated stent. The catheter assembly of the present invention has the feature of containing, in addition to a deployment guide wire, a positioning guide wire and restraint mechanisms that physically permit precise positioning of the angulated stent for deployment.
In one aspect of the invention, there is provided an angulated stent delivery catheter assembly that includes a Y-shaped balloon catheter. The catheter assembly proximal section (the trunk of the Y-shape) includes a catheter tube having a positioning guide wire lumen, an inflation lumen and an elongate tubular member. The elongate tubular member includes a deployment guide wire lumen. The inflation lumen of the catheter proximal section may be configured in a number of ways. For example, the inflation lumen may be configured as an annular lumen positioned concentrically about the elongate tubular member such that the elongate tubular member""s outer surface and the inner surface of the catheter tube form an annular inflation lumen. Alternatively, the inflation lumen may be positioned in a side-by-side configuration with the deployment lumen and the positioning lumen.
The catheter assembly distal section (the branches of the Y-shape) includes a positioning tube (the first branch) and a deployment tube (the second branch). The positioning tube includes a guide wire lumen. The deployment tube may include an elongate tubular member having a guide wire lumen, and an expandable member circumferentially placed about the elongate tubular member. Together, the outer surface of the elongate tubular member and the inner surface of the expandable member define an inflation cavity. An angulated stent may be positioned over the expandable member.
A restraining member is positioned at the catheter assembly distal section and is associated with the deployment tube and positioning tube so that, as the catheter is positioned near a target site in the body lumen, the restraining member assists in properly orienting and maneuvering the deployment tube with the angulated stent positioned thereon into a diseased side branch vessel. The restraining member may have a U-shaped configuration, and may be attached to the positioning tube such that it encompasses the deployment tube and serves to restrict movement of the deployment tube to a predetermined direction. Alternatively, the restraining member may be a sheath having a slit. The sheath may be attached to envelop the entire distal section of the catheter assembly, and the slit may be positioned on the side of the sheath that corresponds to the deployment tube, thereby restricting movement of the deployment tube to a predetermined direction.
In another aspect of the invention, there is provided a method of positioning and deploying an angulated stent into an acutely angulated side branch vessel for treatment of that diseased vessel. The method includes the steps of providing a Y-shaped balloon catheter assembly configured with a positioning tube having a positioning guide wire lumen, a deployment tube having an elongate tubular member including a deployment guide wire lumen, and having an expandable member, and a restraining member. An angulated stent may be mounted on the expandable member of the deployment tube in an orientation that corresponds with the orientation of a diseased side branch vessel. A positioning guide wire may be disposed within the positioning tube, and a deployment guide wire may be disposed within the deployment tube. The positioning guide wire may be introduced into the patient""s vasculature and delivered to a diseased target site within the main vessel. The catheter assembly may be delivered over the positioning guide wire until the catheter distal section is positioned near or at the diseased target site within the main vessel. If necessary, the catheter may be rotated into a desired orientation within the main vessel to align the stent with the orientation of a diseased side branch vessel at the diseased target site. The deployment guide wire may then be maneuvered into the diseased side branch vessel at the target site. Thereafter, the deployment tube may be further advanced over the deployment wire into the side branch vessel. Once the stent is positioned at the target site, the expandable member may be expanded by injecting inflation fluid into the cavity of the expandable member, to deploy the angulated stent. Where subsequent treatment may be required, withdrawal of the catheter and the positioning guide wire allows the deployment guide wire to remain in the side branch providing side branch access for any additional interventional treatment to that vessel. Withdrawal of the catheter with both the positioning and deployment guide wires left in the vessel permits the subsequent use of these two unwrapped wires, should further intervention requiring two wires be necessary.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.